Title: Rice Bran Oil
Additional Names: Oil of rice bran; rice oil
Literature References: Extracted from bran obtained in making white or polished rice (which is actually the endosperm of the seed of Oryza sativa L., Gramineae). Rice bran separated by milling of hulled rice consists of bran, aleurone layer and germ, and contains about 15% oil. The oil is usually obtained by solvent extraction, see J. R. Loeb, N. J. Morris: Abstract Bibliography of the Chemistry, Processing, and Utilization of Rice Bran and Rice Bran Oil, U.S. Dept. of Agriculture, Ms. no AIC-328 (1952 and suppl.). Rice bran contains an unusually active lipase which raises the free fatty acid content on storage. A variety of methods to inhibit this rise can be found in the literature: Williams et al., J. Am. Oil Chem. Soc. 42, 151 (1965). The free fatty acid content of the oil should not exceed 4 to 5%, but may run as high as 70%. Acceptable rice bran oil contains 15-20% of satd and 80-85% unsatd fatty acids as glycerides: Myristic 0.4-1%, palmitic 12-18%, stearic 1-3%, C20-C22 satd 1%, oleic 40-50%, linoleic 29-42%, linolenic trace to 1%, palmitoleic 0.2-0.4%. See also Sreenivasan, J. Am. Oil Chem. Soc. 45, 263 (1968).
Properties: Golden yellow oil, difficult to bleach. Not affected by temporary heating to 160°. d2525 0.916-0.921. nD25 1.470-1.473; nD40 1.465-1.468. Titer (solidification pt) 24-28. Saponification value 181-189. Acid value 4-120 (see above comments on the lipase content of the bran). Iodine value 99-108. Thiocyanogen value 69-76. Hydroxyl value 5-14. Reichert-Meissl value <0.5. Polenské value <0.5. Hehner value 95.3. Unsaponifiable matter 3-5%. The high refractive index is ascribed to the presence of squalene. Also contains other antioxidants such as tocopherols. Miscible with hexane and other fat solvents.
Index of refraction: nD25 1.470-1.473; nD40 1.465-1.468
Density: d2525 0.916-0.921
Use: Soaps, hydrogenated shortenings. Edible oil, also suitable for cosmetics and pharmaceuticals when low in free fatty acids and all the lipase has been deactivated. |